Apoptosis-inducing protein and gene encoding the same

ABSTRACT

An object of the present invention is to provide a protein which induces apoptosis, a base sequence encoding the protein, and an agent for use in the treatment of malignant tumors. The present invention is a protein (ASK1) which has protein kinase activity and enhances SEK1 kinase activity and/or MKK3 kinase activity, or a derivative thereof. Malignant tumors can be treated using the protein according to the present invention or the base sequence encoding the protein.

This application is a national stage entry of PCT/JP97/01348 issued on Apr. 18, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a protein which induces apoptosis (cell death), a gene encoding the same, and a therapeutic agent for malignant tumors.

2. Background Art

The mitogen-activated protein (MAP) kinase signaling cascade, a signal transduction pathway well conserved in cells from yeasts to vertebrates, consists of three distinct members of the protein kinase family, including MAP kinase (MAPK), MAPK kinase (MAPKK), and MAPKK kinase (MAPKKK) (T. Sturgill & J. Wu, Biochim. Biophys. Acta. 1092, 350, 1991; E. Nishida & Y. Gotoh, Trends Biochem. Sci., 18, 128, 1993; B. Errede & D. Levin, Curr. Opin. Cell Biol., 5, 254, 1993; C. Marshall, Curr. Opin. Genet. Dev., 4, 82, 1994). MAPKKK phosphorylates and thereby activates MAPKK, and the activated form of MAPKK in turn phosphorylates and activates MAPK. Activated MAPK translocates to the cell nucleus and regulates the activities of transcription factors and thereby controls expression of various genes (T. Sturgill & J. Wu, Biochim. Biophys. Acta, 1092, 350, 1991; E. Nishida & Y. Gotoh, Trends Biochem. Sci., 18, 128, 1993; B. Errede & D. Levin, Curr. Opin. Cell Biol., 5, 254, 1993; C. Marshall, Curr. Opin. Genet. Dev., 4, 82, 1994).

Recent studies on MAPK signal transduction pathways have shown that at least two distinct MAPKKK-MAPKK-MAPK signal transduction pathways function in mammalian cells (R. Davis, Trends Biochem. Sci., 19, 470, 1994; A. Waskiewicz & J. Cooper, Curr. Opin. Cell Biol., 7, 798, 1995; J. Kyriakis & J. Avruch, J. Biol. Chem., 265, 17355, 1990; B. Derijard et al., Cell, 76, 1025, 1994; M. Yan et al., Nature, 372, 798, 1994; K. Yamaguchi et al., Science, 270, 2008, 1995; J. Kyriakis et al., Nature, 369, 156, 1994; I. Sanchez et al., Nature, 372, 794, 1994; B.

Derijard et al. Science, 267, 682, 1995; S. Matsuda et al., J.

Biol. Chem., 270, 12781, 1995). These two pathways each consist of the Raf-MAPKK-MAPK pathway and the MEKK-SEK1 (or MKK4)-SAPK (or JNK) pathway.

MKK3/MAPKK6 (or MKK6, a close relative of MKK3) and p38 protein kinase are protein kinases corresponding to MAPKK and MAPK, respectively, and are known to form another MAPK signal transduction pathway (R. Davis, Trends Biochem. Sci., 19, 470, 1994; A. Waskiewicz & J. Cooper, Curr. Opin. Cell Biol., 7, 798, 1995; J. Han et al., J. Biol. Chem., 271, 2886, 1996; J. Raingeaud et al., Mol. Cell. Biol., 16, 1247, 1996; T. Moriguchi et al., J. Biol. Chem., 271, 13675, 1996).

Recent studies suggest that the SAPK and/or p38 MAP kinase signaling cascades are involved in at least a part of the signal transduction pathways which induce apoptosis (Z. Xia et al., Science, 270, 1326, 1995; Y. -R. Chen et al., J. Biol. Chem., 271, 631, 1996; N. Johnson et al., J. Biol. Chem., 271, 3229, 1996; M. Verheij et al., Nature, 380, 75, 1996). Apoptosis herein means cell death different from necrosis, namely program cell death. In apoptosis, DNA in each nucleosome is fragmented and the fragmented DNAs can be observed like a ladder by electrophoresis. Furthermore, apoptosis is considered to be involved in autoimmune diseases, HIV infection, neurotic diseases, hepatitis, leukemia, renal diseases, skin diseases, eye diseases and aging as well as cancer degeneration (“Forefront of Research on Apoptosis.” Ed. Masayuki Miura, Shigenobu Toya and Sadatoshi Kizaki, Experimental Medicine, Vol. 13, 1995).

Tumor necrosis factor-α (TNF-α) is known to be a strong cellular apoptosis initiation substance. A recent study has shown that such cellular apoptosis initiation substances activate the SAPK signal transduction system (J. Kyriakis et al., Nature, 372, 794, 1994; J. Raingeaud et al., J. Biol. Chem., 270, 7420, 1995).

However, as far as the inventors know, proteins corresponding to MAPKKK present in upstream of the MKK3-p38 pathway and the SEK1-SAPK pathway, mechanisms of activation of these pathways, and mechanisms of apoptosis through these pathways have not been reprted.

SUMMARY OF THE INVENTION

The inventors have now identified a novel mammalian protein (ASK1) corresponding to MAPKKK, which activates the MKK3-p38 signal transduction pathway as well as the SEK1-SAPK signal transduction pathway. The inventors have also found that proinflammatory cytokines activate ASK1 and the activated ASK1 is involved in cellular induction of apoptosis through the SEK1-SAPK and MKK3-p38 signaling cascades. Furthermore, the inventors found that a dominant-negative mutant of ASK1 inhibits apoptosis induced by TNF-α. The present invention is based on these findings.

Accordingly, an object of the present invention is to provide a protein which induces apoptosis, a base sequence encoding the protein, a vector comprising the base sequence, a host comprising the vector and a method for producing the protein.

Another object of the present invention is to provide an agent for use in the treatment of malignant tumors or a gene therapy agent for use in the treatment of malignant tumors.

A further object of the present invention is to provide a partial peptide of the apoptosis-inducing protein and an antibody against the apoptosis-inducing protein.

The protein according to the present invention is a protein which has a protein kinase activity and enhances the SEK1 kinase activity and/or MKK3 kinase activity, or derivatives thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the deduced amino acid sequence of human ASK1. The putative translation start sites for two independent clones (clone 20 and clone 27) are indicated by arrows. The protein kinase domain is shown in boldface. An FKBP-type peptidyl-prolyl cis-trans isomerase motif present in the N-terminal non-catalytic portion is underlined. Abbreviations for the amino acid residues are as follows: A, Ala: C, Cys; D, Asp; E, Glu; F, Phe; G, Gly; H: His; I: Ile; K: Lys; L: Leu; M: Met; N: Asn; P: Pro; Q: Gln; R: Arg; S, Ser; T, Thr; V, Val; W, Trp; and Y, Tyr.

FIG. 2 shows the phylogenetic relationship of the MAPKKK family.

FIG. 3 shows RNA blots (electrophoretic photographs) demonstrating tissue distribution of ASK1.

FIG. 4 shows photographs demonstrating the growth (colony formation) of yeast mutant strain TM257-H1 with ASK1 gene expression (ASK1, ASK1(K709R)) or without ASK1 gene expression (vector). Tests were carried out in the presence or absence of 1.5 M sorbitol.

FIG. 5 is an electrophoretic photograph showing the activation of MAPKK and MAPK by ASK1 in vivo. The activation is indicated by the phosphorylation of substrate proteins. The position of each substrate protein is shown by a bracket or an arrowhead. The fold increase of kinase activity caused by coexpression of ASK1 is indicated above each lane; this figure is an average of three independent experiments. Molecular weights are indicated in kilodaltons (kDa).

FIG. 6 is an electrophoretic photograph showing in vitro activation of MAPKKs by ASK1. COS7 cells were transfected with pcDNA3-ASK1 and cell lysates were subjected to immunoprecipitation with preimmune serum (Mock ppt) or antiserum to ASK1 (ASK1 ppt). The immune complex or a buffer solution (Buffer) was first incubated with (+) or without (−) His-MAPKK, His-SEK1, His-MKK3, or His-MAPKK6 MAPKK, and then the kinase activity of individual MAPKK was measured with the substrate GST-kinase-negative MAPK for MAPKK and His-kinase negative MPK2 for SEK1, MKK3, and MAPKK6. In the photograph, “KN-MAPK” represents GST-kinase negative MAPK and “KN-MPK2” represents His-kinase negative MPK2.

FIG. 7 is an electrophoretic photograph showing ZnCl₂-dependent expression of ASK1 and ASK1(K709R) in stably transfected Mv1Lu cells (transfection).

FIG. 8 is a graph showing ASK1-dependent inhibition of [³H] thymidine incorporation. ▪: Vector alone, : ASK1, ◯: ASK1 (K709R). This data represents three independent experiments. Error bars represent the standard deviations.

FIG. 9 is an electrophoretic photograph showing dose-dependent ASK1 protein expression (top) and ASK1 activation (bottom) by ZnCl₂ induction. “no-IP” represents the case where the cell lysate was used as an enzyme sample without immunoprecipitation.

FIG. 10 is an electrophoretic photograph showing ASK1-dependent activation of endogenous SAPK (top) and p38 (bottom). The positions of p54 and p46 SAPK (top) and ATF2 (bottom) are indicated by arrowheads and an arrow, respectively.

FIG. 11 shows phase-contrast microscopic photographs of representative cell morphology taken at the same magnification. These photographs show ASK1-dependent cell death. (Top) Cells were incubated in an MEM medium containing 1% FBS in the presence or absence of 100 μM ZnCl₂ for 26 hours. (Bottom) Cells were incubated in an MEM medium without FBS in the presence or absence of 100 μM ZnCl₂ for 25 hours. The cells were then stained by the TUNEL method. Apoptotic cells are shown by dark brown staining. Photographs were taken at a higher magnification than in the top panel.

FIG. 12 is an electrophoretic photograph showing ASK1-dependent DNA fragmentation.

FIG. 13 shows activation, with time, of ASK1 by TNF-α in various cells. (Top) Values of ASK1 activity in Mv1Lu cells transfected with ASK1 are given as relative values. The results are mean values from at least five independent experiments. Error bars indicate the standard deviations. (Bottom) The figure shows ASK1 activity, with time (minutes), in ASK1-transfected Mv1Lu cells and non-ASK1 transfected 293 cells and A673 cells treated with TNF-α.

FIG. 14 shows TNF-αdose-dependent activation of ASK1. Values for ASK1 activity are the averages from at least five independent experiments. Error bars indicate the standard deviations.

FIG. 15 is an electrophoretic photograph showing that DNA fragmentation in 298 cells stimulated by TNF-α in the presence or absence (none) of actinomycin D is inhibited by transfection of ASK1(K709R).

FIG. 16 is an electrophoretic photograph showing that DNA fragmentation in Jurkat T cells stimulated by TNF-α in the presence or absence (none) of actinomycin D is inhibited by transfection with ASK1(K709R). In the Figure, “none” represents the case where cells are not transfected or not stimulated.

DETAILED DESCRIPTION OF THE INVENTION

Definition

The term “amino acid” in the present invention includes both optical isomers, i.e., the L-isomer and the D-isomer. Thus, the term “protein” herein means not only proteins constituted solely by L-amino acids but also proteins comprising D-amino acids in part or in total.

Furthermore, the term “amino acid” herein includes not only the twenty α-amino acids which constitute natural proteins but also other α-amino acids as well as β-, γ, and δ-amino acids, non-natural amino acids, and the like. Thus, amino acids with which proteins are substituted or amino acids inserted into proteins as shown below are not restricted to the twenty α-amino acids which constitute natural proteins but may be other α-amino acids as well as β-, γ- and δ-amino acids, non-natural amino acids, and the like. Such β-, γ and δ-amino acids include β-alanine, γ-aminobutyric acid or ornithine. The amino acids other than those constituting natural proteins, or the non-natural amino acids include 3,4-dihydroxyphenylalanine, phenylglycine, cyclohexylglycine, 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid or nipecotinic acid.

In this specification, a specific mutation is notated by the original amino acid residue (one letter) first, the position number second and the amino acid residue after substitution (one letter) third. For example, “K709R” means K (Lys: lysine), the amino residue at position 709, is substituted by R (Arg: arginine).

The term “protein” as used herein includes peptides. Furthermore, the expression “protein according to the present invention” includes derivatives of the protein.

Apoptosis-inducing Protein

The apoptosis-inducing protein according to the present invention is a protein which has a protein kinase catalytic region and enhances SEK1 kinase activity and/or M3 kinase activity, or derivatives thereof.

The apoptosis-inducing protein is not specifically restricted to any source but it may be derived from a mammal including a human, or any other sources.

The apoptosis-inducing protein has protein kinase activity. The term “protein having protein kinase activity” in the present invention means a protein which is evaluated by those skilled in the art to have protein kinase activity, for example, a protein which is evaluated to have protein kinase activity when examined under the same conditions as in Example 1. The term “protein kinase activity” includes serine/threonine protein kinase activity.

The apoptosis-inducing protein enhances the SEK1 kinase activity and/or MKK3 kinase activity. The term “protein enhancing the SEK1 kinase activity and/or M3 kinase activity” in the present invention means a protein which is evaluated by those skilled in the art to enhance these activities, for example, a protein which is evaluated to enhance the SEK1 kinase activity and/or MKK3 kinase activity when examined under the same conditions as in Examples 3, 4 and 6.

The protein according to the present invention is characterized by the induction of apoptosis. This apoptosis is mediated through the enhancement of the SAPK or JNK and/or p38 activity.

The enhancement of the SEK1 kinase activity and/or MKK3 kinase activity by the protein according to the present invention is accelerated by tumor necrosis factors (TNFs). An example of the tumor necrosis factor herein is TNF-α.

The term “derivatives of proteins” as used herein includes proteins in which the amino groups at the amino terminals (N-terminals) or all or a part of the amino groups of the side chains of the amino acids, and/or the carboxyl groups at the carboxyl terminals (C-terminals) or all or a part of the carboxyl groups of the side chains of the amino acids, and/or the functional groups other than the amino groups and carboxyl groups of the side chains of the amino acids (e.g., hydrogen, thiol group and amido group) have been modified by other appropriate substituents. The modification by other appropriate substituents is carried out, for example, to protect functional groups in the protein, to improve safety and tissue-translocation of the protein or to enhance protein activity.

The derivatives of the proteins include:

(1) proteins in which a part or all of the hydrogen atoms of the amino groups at the amino terminals (N-terminals) or the amino groups of the side chains of the amino acids are replaced by substituted or unsubstituted alkyl groups (which may be straight chain, branched chain, or cyclic) (e.g., methyl group, ethyl group, propyl group, isopropyl group, isobutyl group, butyl group, t-butyl group, cyclopropyl group, cyclohexyl, and benzyl group), substituted or unsubstituted acyl groups (e.g., formyl group, acetyl group, caproyl group, cyclohexylcarbonyl group, benzoyl group, phthaloyl group, tosyl group, nicotinoyl group, and piperidinecarbonyl group), urethane-type protective groups (e.g., p-nitrobenzyloxycarbonyl group, p-methoxybenzyloxycarbonyl group, p-biphenylisopropyl-oxycarbonyl group, and t-butoxycarbonyl group), or urea-type substituents (e.g., methylaminocarbonyl group, phenylcarbonyl group, and cyclohexylaminocarbonyl group).

(2) proteins in which a part or all of the carboxyl groups at the carboxyl terminals (C-terminals) or the carboxyl group of the side chains of the amino acids are esterified (for example, the hydrogen atom(s) are replaced by a methyl group, ethyl group, isopropyl group, cyclohexyl group, phenyl group, benzyl group, t-butyl group, or 4-picolyl group), or amidated (for example, unsubstituted amides or C1-C6 alkyl amides (e.g., methylamides, ethylamides and isopropylamides) are formed); and

(3) proteins in which a part or all of the functional groups other than the amino groups and carboxyl groups of the side chains of the amino acids (e.g., hydrogen, thiol group and amino group) are modified by substituents similar to those for the abovementioned amino groups or a trityl group.

Examples of the protein according to the present invention include proteins comprising the amino acid sequence of SEQ ID NO: 1 having one or more additions, insertions, substitutions and/or deletions, which have protein kinase activity and which enhance SEK1 kinase activity and/or MKK3 kinase activity. The terms “addition,” “insertion,” “substitution” and “deletion” as used herein refer to those that do not damage the capacity to enhance the protein kinase activity and SEK1 kinase activity and/or MKK3 kinase activity of the protein comprising the amino acid sequence of SEQ ID NO: 1. One or more additions, insertions, substitutions and deletions can be introduced.

The protein according to the present invention is characterized by the enhancement of the SEK1 kinase activity and/or MKK3 kinase activity. SEK1 and MKK3 are known to be involved in apoptosis. Therefore, the protein according to the present invention is useful in elucidating the mechanisms of cell functions such as apoptosis.

The present invention provides a protein comprising the amino acid sequence of SEQ ID NO: 1 having one or more additions, insertions, substitutions and/or deletions and lacking protein kinase activity, or a derivative thereof, (dominant-negative mutants). One or more additions, insertions, substitutions and deletions can be introduced.

This protein can be obtained by modifying a protein which has protein kinase activity and enhances SEK1 kinase activity and/or MKK3 kinase activity in such a manner so as to destroy the protein kinase activity. An example of such modification is a substitution: K709R.

This modified protein inhibits apoptosis caused by TNF-αas described in Examples thereinafter. Therefore, this modified protein is useful in elucidating the living phenomena in which ASK1 is involved in.

Base Sequence

The present invention provides a base sequence encoding the protein according to the present invention. An example of the base sequence encoding the protein according to the present invention is a sequence having a part or all of the DNA sequence of SEQ ID NO: 2. Base sequences in this specification mean both DNA sequences and RNA sequences.

When the modified amino acid sequence is given, the base sequence encoding such amino acid sequence is easily determined, and a variety of base sequences encoding the amino acid sequence described in SEQ ID NO: 1 can be selected. The base sequence encoding the protein according to the present invention thus means, in addition to a part or all of the DNA sequence described in SEQ ID NO: 2, another sequence encoding the same amino acid sequence and having degenerate codon(s) in the DNA sequence. Furthermore, this base sequence includes RNA sequences corresponding to such DNA sequences.

The base sequence according to the present invention may be derived naturally or obtained entirely by synthesis. It may also be synthesized using a part of a naturally occurring sequence. DNAs may typically be obtained by screening a chromosome library or a cDNA library in accordance with a conventional manner in the field of genetic engineering, for example, by screening with an appropriate DNA probe obtained based on information of the partial amino acid sequence.

Examples of the base sequence encoding the protein according to the present invention include the DNA sequence 268-4392 of SEQ ID NO: 2 (corresponding to the open reading frame).

Vector and Transformed Host Cell

The present invention provides a vector comprising the abovementioned base sequence in such a manner that the vector can be replicable and express the protein encoded by the base sequence in a host cell. In addition, the present invention provides a host cell transformed by this vector. This host-vector system is not particularly restricted and fusion protein expression systems with other proteins can also be used. Examples of the fusion protein expression system include those using MBP (maltose binding protein), GST (glutathione-S-transferase), HA (hemagglutinin), His (hexahistidine), myc, Fas, and the like.

Examples of the vector include plasmid vectors (e.g., expression vectors for prokaryotic cells, yeasts, insect cells, and animal cells), virus vectors (e.g., retrovirus vectors, adenovirus vectors, adeno-associated virus vectors, herpesvirus vectors, Sendai virus vectors, HIV vectors, and vaccinia virus vectors), and liposome vectors (e.g., cationic liposome vectors).

In order to express a desired amino acid sequence practically by introducing the vector according to the present invention into a host cell, the vector may contain, in addition to the base sequence according to the present invention, other sequences for controlling the expression (e.g., promoter sequences, terminator sequences and enhancer sequences) and gene markers for selecting microorganisms, insect cells, animal culture cells, or the like (e.g., neomycin resistance genes and kanamycin resistance genes). Furthermore, the vector may contain the base sequence according to the present invention in a repeated form (e.g., in tandem). These base sequences may also be introduced in a vector according to the conventional manner, and microorganisms, insect cells, animal cultured cells, or the like may be transformed by the vector based on the method conventionally used in this field.

The vector according to the present invention may be constructed based on the procedure and manner which have been conventionally used in the field of genetic engineering.

Furthermore, examples of the host cell include Escherichia coli, yeasts, insect cells and animal cells such as COS cells (e.g., COS7 cells), mink lung epithelial cells (e.g., Mv1Lu), lymphocytes, fibroblasts, CHO cells, blood cells, tumor cells, and the like.

The transformed host cells are cultured in an appropriate medium, and the protein according to the present invention may be obtained from the culture product. Thus, another aspect of the present invention provides a process for preparing the protein according to the present invention. The culture of the transformed host cell and culture conditions may be essentially the same as those for the cell to be used. In addition, the protein according to the present invention may be recovered from the culture medium and purified in the conventional manner.

The present invention can be applied in the gene therapy of malignant tumors (e.g., leukemia cells, digestive tract carcinoma cell, lung carcinoma cells, pancreas carcinoma cells, ovary carcinoma cells, uterus carcinoma cells, melanoma cells, brain tumor cells, etc.) by introducing a vector having the base sequence according to the present invention into cancer cells of an organism including humans using an appropriate method to express the protein according to the present invention, i.e., by transforming the cancer cells of cancer patients in situ. For example, when the protein according to the present invention is expressed in an organism including humans, in particular, in malignant tumor cells, apoptosis is induced causing the malignant tumor to shrink, thereby enabling treatment of the tumor (see Example 5).

As for the vectors for gene therapy, see Fumimaro Takahisa, Experimental Medicine (extra edition), Vol. 12, No. 15, “Forefront of Gene Therapy” (1994).

Use and Pharmaceutical Composition

The protein according to the present invention has protein kinase activity and enhances SEK1 kinase activity and/or MKK3 kinase activity (Examples 3 and 4). Furthermore, the protein according to the present invention induces apoptosis of immortalized cells (Example 5). Thus, the protein according to the present invention is useful in suppressing tumorigenesis and/or metastasis in malignant tumors.

Therefore, according to the present invention, an agent for use in the treatment of malignant tumors comprising the protein according to the present invention and a pharmaceutically acceptable carrier is provided. The term “treatment” in the present invention also refers to “prevention.” Examples of malignant tumors include leukemia (for example, myelocytic leukemia, lymphocytic leukemia such as Burkitt lymphoma), digestive tract carcinoma, lung carcinoma, pancreas carcinoma, ovary carcinoma, uterus carcinoma, brain tumor, malignant melanoma, other carcinomas, and sarcomas.

The agent for use in the treatment of malignant tumors according to the present invention may be administered orally or parenterally (e.g., intramuscular injection, intravenous injection, subcutaneous administration, rectal administration, transdermal administration, nasal administration, and the like), preferably orally. The pharmaceutical agent may be administered to a human and other animals in a variety of dosage forms suited for oral or parenteral administration.

The agent for use in the treatment of malignant tumors can be formulated in a variety of form including oral agents such as tablets, capsules, granules, dispersible powders, pills, fine particles and troches, injections such as intravenous injections and intramuscular injections, rectal agents, fatty suppositories and aqueous suppositories, for example, depending on their intended uses. These preparations may be prepared according to methods well known in the art with conventional excipients, fillers, binding agents, wetting agents, disintegrating agents, surfactants, lubricants, dispersing agents, buffering agents, preservatives, dissolution aids, antiseptics, flavorings, analgesic agents and stabilizing agents. Examples of the abovementioned possible nontoxic additives to be used include lactose, fructose, glucose, starch, gelatin, magnesium carbonate, synthetic magnesium silicate, talc, magnesium stearate, methylcellulose, carboxymethylcellulose or a salt thereof, gum arabic, polyethylene glycol, syrup, Vaseline, glycerine, ethanol, propylene glycol, citric acid, sodium chloride, sodium sulfite, and sodium phosphate.

The content of the protein according to the present invention in a pharmaceutical agent varies depending on its dosage forms. The composition may contain about 1-50% by weight, preferably about 1-20% by weight, of the protein.

The dose of the protein for the treatment of malignant tumors may appropriately be determined in consideration of its uses and the age, sex and condition of a patient, and is desirably in the range of about 0.1-500 mg, preferably about 0.5-50 mg, per day for an adult, which may be administered at once or divided into several portions a day.

According to the present invention, a base sequence encoding the protein according to the present invention or a vector comprising the base sequence may be used to suppress tumorigenesis and/or metastasis of malignant tumors by transforming a target cell. In other words, the base sequence and vector can be used as a gene therapeutic agent for use in the treatment of malignant tumors (the gene therapy agent). The method of administration, effective dosage, possible carriers to be included, and other parameters of a gene therapeutic agent can conform to those for an antitumor agent.

The gene therapeutic agent according to the present invention can be administered to a mammal, including a human, and other animals by the HVJ liposome method (Kaneda, Experimental Medicine, Vol. 12, No. 2, 78(184), 1994; Morishita, et al., Experimental Medicine, Vol. 12, No. 15, 158(1928), 1994), a method in which the base sequence according to the present invention is administered as is by injection or the like, the calcium phosphate method, the DEAE-dextran method, the electroporation method, the gene gun method (T. M. Klein et al., Bio/Technology 10, 286-291, 1992), the lipofection method (Nabel et al., Science 244, 1285, 1990), a method using an appropriate vector (e.g., adenovirus vector, adeno-associated virus vector, herpes virus vector, vaccinia virus vector, and retrovirus vector), or the like.

In considering the local or temporary induction of apoptosis, the gene therapy agent according to the present invention is preferably administered in such a manner that ASK1 is transiently present in the body. Examples of such a manner include parenteral administration methods such as administering the base sequence according to the present invention as is by injection or the like, the lipofection method, the HVJ liposome method, a method using an adenovirus vector, and a method using a vaccinia virus vector.

Another aspect of the present invention provides a use of the protein, base sequence or vector, in particular, a use for the manufacture of a medicament.

Still another aspect of the present invention provides a method for treating malignant tumors in mammals comprising administrating the protein, base sequence or vector according to the present invention. The effective dosages, methods of administration and dosage forms can apply for this method.

Peptide and Antibody

The present invention provides a peptide consisting of the amino acid sequence 654-669 of SEQ ID NO: 1 and a peptide comprising the amino acid sequence 654-669 of SEQ ID NO: 1.

Examples of the peptide comprising the amino acid sequence 654-669 of SEQ ID NO: 1 include a peptide in which an optional amino acid sequence is added to the N-terminal and/or C-terminal of said amino acid sequence, including the protein according to the present invention.

The peptide can be used as an antigen to obtain an antibody against the protein according to the present invention. Furthermore, the protein according to the present invention is closely involved in mechanisms of apoptosis as mentioned above. Therefore, the protein according to the present invention is useful in elucidating these mechanisms of apoptosis.

The present invention provides the antibody against the peptide. The antibody in the present invention includes a polyclonal antibody and a monoclonal antibody.

The antibody according to the present invention can be produced by a method generally known by those skilled in the art. For example, the polyclonal antibody can be obtained by injecting the abovementioned peptide into an animal (e.g., a rabbit, goat, rat, mouse, and sheep) with an optional carrier (e.g., bovine serum albumin) and purifying the serum of the animal after a certain period. The monoclonal antibody can be prepared by the hybridoma fusion technique. For example, see the following literature for reference: Kohler and Milstein, Nature, 256: 495-97, 1975; Brown et al., J. Immunol., 127(2), 539-46, 1981; Brown et al., J. Biol. Chem., 255, 4980-83, 1980; Yeh et al., Proc. Natl. Acad. Sci. (USA), 76(6), 2927-31, 1976; and Yeh et al., Int. J. Cancer, 29, 269-75, 1982; Zola et al., in Monoclonal Hybridoma Antibodies: Techniques and Applications, Hurell (ed.), pp. 51-52 (CRC Press, 1982).

The peptide according to the present invention is a part of the amino acid sequence of the protein according to the present invention. Therefore, a specific reaction (i.e., immuno cross reaction) of the antibody according to the present invention can be an index for the presence of the protein according to the present invention.

Thus, another aspect of the present invention provides a protein which can be recognized by the antibody according to the present invention, and the protein according to the present invention which can be recognized by the antibody.

EXAMPLE Example 1

Cloning of ASK1 cDNA by Polymerase Chain Reaction (PCR) Method and Determination of Amino Acid Sequence of ASK1

(1) Isolation of cDNA

A degenerate PCR-based strategy was used in an attempt to obtain a novel serine/threonine kinase cDNA according to the method described in P. ten Dijke et al., Oncogene, 8, 2879, 1993; P. Franzen et al., Cell, 75, 681, 1993, and P. ten Dijke et al., Science, 264, 101, 1994.

As a result, several human cDNA fragments encoding more distantly related protein kinases whose functions are unknown along with the recipient-type serine/threonine kinase family, were obtained.

First, a PCR fragment was obtained using a set of PCR primers derived from the conserved subdomains VII and VIII of the serine/threonine kinase family (S. Hanks et al., Science, 241, 42, 1988). Using this fragment, a corresponding nearly full-length cDNA clone was isolated (the serine/threonine kinase encoded by this cDNA is hereinafter referred to as activator of SEK1 and MKK3 (ASK1) because of its characteristics).

More specifically, an amplified oligo(dT)-primed λgt 11 cDNA library from human erythroleukemia (HEL) cells (M. Poncz et al., Blood, 69, 219, 1987) was screened with a ³²P-labeled PCR fragment. Hybridization and purification of positive bacteriophage were performed as described in H. Ichijo et al., J. Biol. Chem., 268, 14505, 1993. Base sequencing was done on both strands with a Sequenase DNA sequencing kit (U.S. Biochemical Corp.). Among 18 clones obtained, the three longest clones (clones 20, 27 and 72) were entirely sequenced. The sequence of clone 72 started from the middle of the open reading frame and ended by a stretch of poly A. The sequences of clones 20 and 27 covered the 5′ part of ASK1 cDNA, and the overlapping parts with clone 72 were identical in sequence. The ASK1 cDNA sequence, combining the clone 20 and clone 72, yielded a 4533-base pair sequence with an ATG codon starting at position 268 followed by a 4125-bp open reading frame encoding a protein consisting of 1375 amino acids (FIG. 1). This protein (ASK1 protein) has an estimated molecular weight of 154,715 Da.

On the other hand, another clone (clone 27) was obtained in which an open reading frame starts from the site corresponding to an amino acid at position 375 of clone 20. Because clone 27 contained a 4-bp deletion at position 805 to 808 of ASK1 cDNA, in-frame upstream stop codons were formed.

The serine/threonine kinase domain of ASK1 was found in the middle part of the ASK1 protein and had long N-terminal and C-terminal flanking sequences (FIG. 1). Furthermore, RNA blot analysis revealed a single 5-kb transcript that was expressed in various human tissues (FIG. 3). Blots with mRNAs from various human tissues (Clontech) were probed with ASK1 cDNA labeled by random priming.

(2) Homology Search by Database

A database search of ASK1 sequence outside its kinase domain showed that a short amino acid sequence in the N-terminal part contains a motif for an FK506-binding protein (FKBP)-type peptidyl-prolyl cis-trans isomerase (FIG. 1, underlined). In contrast, the kinase domain of ASK1 has evident sequence homology with members of the MAPKKK family. The degree of homology was 30.0% with MEKK1 in mammal and 32.3% and 30.4% with SSK2 and STE11 in Saccharomyces cerevisiae, respectively.

Phylogenetic comparison suggested that ASK1 is distantly related to mammalian MAPKKKs (RAF-1, KSR-1, TAK-1, and TPL-2) but most closely related to the SSK2/SSK22 family of yeast MAPKKK protein, which are upstream regulator proteins of yeast HOG1 MAPK (T. Maeda et al., Science, 269, 554, 1995). (FIG. 2).

Comparison of amino acid sequences between the kinase domain of ASK1 and kinase domains of other MAPKKKs was carried out using the clustal computer alignment program of laser gene program (DNASTAR) (D. Higgins & P. Sharp, Comput. Appl. Biosci., 5, 151, 1989).

Example 2

Molecular Genetic Analysis of ASK1 Kinase Activity Using Yeast

Overall structures of ASK1 and yeast MAPKKKs, SSK2/SSK22, are different (namely, the kinase domain of SSK2 or SSK22 is located in the C-terminal part of these proteins (T. Maeda et al., Science, 269, 554, 1995)). However, it was of interest to examine whether ASK1 might act as a functional kinase in yeast and thereby complement the loss of yeast MAPKKK.

First, ASK1 cDNA was introduced into a yeast expression vector pNV11 (H. Shibuya et al., Nature, 357, 700, 1992), and whether ASK1 can restore SSK2 or SSK22 MAPKK signal deletion in a yeast mutant strain TM257-H1 (ssk2Δ, ssk22Δ, sho1Δ) ( ), which grows in a normal YPD medium but not in a hyperosmotic medium was investigated. In this connection, SHO1 is an SH3 domain-containing trans-membrane osmosensor that relates to another signaling pathway leading to various hyperosmolarity responses by way of HOG1 activation independently of SSK2/SSK22. Single or double mutant strains of SHO1, SSK2 or SSK22 are resistant to hyperosmotic medium. However, it is known that if SHO1, SSK2 and SSK22 are simultaneously destroyed, the yeast cells are unable to grow in hyperosmotic medium.

Accordingly, transformants were tested for growth in the presence of 1.5 M sorbitol (FIG. 4). Specifically, five independent transformants were selected and grown on YPD plates in the presence or absence of 1.5 M sorbitol. Photographs in FIG. 4 were taken after the growth for 6 days at 30° C.

Transformants with PNV11 vector alone or ASK1(K709R) (a mutant strain in which kinase catalytic activity was inactivated by substituting Lys 709 with Arg) vector were also tested.

Results showed that expression of ASK1, but neither vector alone nor ASK1 (K709R), complemented TM257-H1 growth in the hyperosmotic environment (FIG. 4). ASK1 could not restore the osmotic response in a PBS2 (downstream target protein of SHO1, SSK2, and SSK2 (Maeda, T. et al., Science, 269, 554, 1995))-defective yeast strain (data not shown). This observation strongly suggests that ASK1 activity observed in TM257-H1 was mediated by the PBS-HOG1 signaling pathway but not by any pathway other than the HOG1 activation.

These results, together with the fact that the mammalian counterpart of yeast HOG1 is p38 MAP kinase (J. Rouse et al., Cell, 78, 1027, 1994; J. Han et al., Science, 265, 808, 1994; J. Lee et al., Nature, 372, 739, 1994), suggested that ASK1 may be a novel mammalian MAPKKK and involved in activation of MKK3-p38 signal transduction pathway by phosphorylating MKK3.

Example 3

Cell Biological Analysis of ASK1 Kinase Activity Using Mammalian Cells

To investigate whether ASK1 may function as an MAPKKK in mammalian cells, an ASK1 plasmid was transfected into COS7 cells together with known MAPK and MAPKK expression plasmids (FIG. 5). All the MAPK and MAPKK constructs were hemagglutinin (HA) epitope-tagged, expressed with or without ASK1, and immunoprecipitated with antibody to HA. Specifically, the following procedure was used.

The cDNAs encoding Xenopus MAPK (Y. Gotoh et al., EMBO J., 10, 2661, 1991) and Xenopus MAPKK (H. Kosako et al., EMBO J., 12, 787, 1993) were cloned as previously described. Coding regions for rat SAPKα (J. Kyriakis et al., Nature, 369, 156, 1994), human p38 (J. Han et al., Biochim. Biophys. Acta, 1265, 224, 1995), mouse SEK1 (I. Sanchez et al., Nature, 372, 794, 1994), and human MKK3 (B. Derijard et al., Science, 267, 682, 1995) were amplified by PCR method. An HA tag was introduced into the BglII-EcoRI sites of a mammalian expression vector pSRα456 (Y. Takebe et al., Mol. Cell. Biol., 8, 466, 1988), yielding pSRα-HA1. The cDNAs encoding MAPK, SAPKα, p38, MAPKK, SEK1, and MKK3 were subcloned into the BglII site of pSRα-HA1. ASK1 cDNA was introduced into another mammalian expression vector, pcDNA3 (Invitrogen). For transient expression, COS7 cells were transfected with lipofectamine (Life Technologies) according to the manufacturer's instructions. For preparing extracts, cell were lysed in a buffer solution (20 mM tris-HCl (pH 7.5), 12 mM β-glycerophosphate, 150 mM NaCl, 5 mM EGTA, 10 mM NaF, 1% Triton X-100, 0.5% deoxycholate, 3 mM dithiothreitol (DTT), 1 mM sodium vanadate, 1 mM phenylmethylsufonyl fluoride (PMSF), and aprotinin (20 μg/ml)). Cell extracts were clarified by centrifugation at 15,000 g for 10 min.

For immunoprecipitation, the supernatants were incubated with monoclonal antibody to HA (12CA5) for 1 hour at 4° C. After the addition of protein A-Sepharose (Pharmacia Biotech), the lysates were incubated for an additional 1 hour. The beads were washed twice with a solution (500 mM NaCl, 20 mM tris-HCl (pH 7.5), 5 mM EGTA, 1% Triton X-100, 2 mM DTT, and 1 mM PMSF), then twice with a solution (150 mM NaCl, 20 mM tris-HCl (pH 7.5), 5 mM EGTA, 2 mM DTT, and 1 mM PMSF), and subjected to kinase assays.

The precipitated immune complexes were subjected to a phosphorylation assay. In the assay, exogenous proteins were added as substrates. The substrate proteins used were myelin basic protein (MBP) (Sigma) for MAPK, c-Jun for SAPK, ATF-2 for p38, kinase-negative MAPK for MAPKK, and kinase-negative p38 (MPK2) for SEK1 and MKK3. ATF2 used herein was prepared according to the method previously described (S. Gupta et al., Science, 267, 389-393, 1995). Hexahistidine (His)-tagged c-Jun (S. Matsuda et al., J. Biol. Chem., 270, 12781, 1995) and glutathione-S-transferase (GST)-kinase-negative Xenopus MAPK (K57D) were prepared as described in H. Kosako et al., EMBO J., 12, 787, 1993. MPK2 (J. Rouse et al., Cell, 78, 1027, 1994), a Xenopus counterpart of mammalian p38, was used as a substrate protein for SEK1 and MKK3 in the assay.

His-tagged kinase-negative MPK2 (K54R) was prepared according to the method described in T. Moriguchi et al., J. Biol. Chem., 270, 12969, 1995. To measure the activity to phosphorylate MBP, c-Jun, ATF2, kinase-negative MAPK, and kinase-negative MPK2, the immune complex was incubated for 30 minutes at 30° C. with 3 μg of each substrate protein in a final volume of 25 μl of a solution (20 mM Tris-HCl (pH 7.5), 10 mM MgCl₂, 100 μM [γ-³²P]ATP (0.3 μCi)). The reaction was stopped by addition of Laemmli's sample buffer and boiling. After SDS-polyacrylamide gel electrophoresis (PAGE), phosphorylation of these proteins was quantified with an image analyzer (FujiX BAS2000).

Results showed that ASK1 expression induced 7.6- and 5.0-fold activation of SAPK and p38 MAP kinase, respectively, but only weakly activated MAPK (FIG. 5).

Furthermore, ASK1 activated MKK3 and SEK1 up to 11.8- and 7.0-fold, respectively. In contrast, no detectable activation of MAPKK was observed (FIG. 5).

Example 4

In Vitro-coupled Kinase Assay with Recombinant Proteins

To investigate whether the MKK3 activation observed in FIG. 5 was a direct effect by ASK1, an in vitro-coupled kinase assay with recombinant SEK1, MKK3, MAPKK6, and recombinant kinase-negative p38 (MPK2) proteins was used. In this Example, ASK1 expressed in COS7 cells was immunoprecipitated with polyclonal antibody as described in Example 3, and the resulting immune complex was used as an ASK1 enzyme standard. The anti-ASK1 polyclonal serum used in the immunoprecipitation was raised against the peptide sequence (SEQ ID NO:3)(TEEKGRSTEEGDCESD), corresponding to amino acids 654 to 669 of ASK1, that was coupled to keyhole limpet hemocyanin by a glutaraldehyde method, mixed with Freund's adjuvant, and used to immunize rabbits according to the method described in H. Ichijo et al., J. Biol. Chem., 270, 7420, 1995. The coupled kinase assay was carried out using recombinant SEK1, MKK3, MAPKK6, and recombinant kinase-negative p38 proteins together with this immune complex according to the following procedure.

His-tagged Xenopus MAPKK and human MKK3 were expressed in Escherichia coli and purified as described in Y. Gotoh et al., Oncogene, 9, 1891, 1994. To measure the activity of an immune complex to activate MAPKK or MKK3, 0.2 μg of His-MAPKK or His-MKK3 was first incubated with the immune complex for 15 minutes at 30° C. in a final volume of 25 μl of a solution (20 mM Tris-HCl (pH 7.5), 10 mM MgCl₂, and 100 μM ATP). Subsequently, 0.3 μCi of [γ32P] ATP and 3 μg of GST-kinase-negative MAPK (to MAPKK) or His-kinase-negative MPK2 (to MKK3) were incubated in the same buffer solution (final volume, 35 μl) for 7 minutes at 25° C. Samples were then analyzed by SDS-PAGE and image analyzer. Results are shown in FIG. 6.

ASK1 immunoprecipitates from COS7 cells strongly activated SEK1, MKK3, and MAPKK6 activity (greater than 40-fold for each), and phosphorylation of p38 was observed only when ASK1 was present in the kinase assay. ASK1-dependent phosphorylation of p38 was further confirmed to result in the activation of p38 using wild-type p38 and ATF2. In contrast, ASK1 weakly activated MAPKK (2.2-fold) even in the presence of MAPKK.

When Raf was used as MAPKKK for a positive control, a 27.8-fold activation of MAPKK was observed (date not shown). These results (Example 4) and the results in Example 3 indicated that ASK1 is a novel MAPKKK, which selectively activates the SEK1-SAPK and MKK3/MAPKK6-p38 pathways.

Example 5

Induction of Apoptosis by ASK1 Expression

(1) Confirmation of ASK Expression

The biological activity of ASK1 was investigated using mink lung epithelial (Mv1Lu) cell lines that were stably transfected with metallothionein promoter-based expression plasmids. To avoid the possibility that constitutively expressed ASK1 might induce cell death, resulting in a failure to obtain stable transformants, a metallothionein-inducible promoter system was used.

ASK1 and ASK1(K709R) cDNA were subcloned into pMEP4 vector (Invitrogen) at convenient enzyme cleavage sites. Transfection of cDNAs was done with Transfectam (Promega) according to the manufacturer's instructions. Selection by hygromycin B was done by the method described in M. Saitoh et al., J. Biol. Chem., 271, 2769, 1996. Several independent clones were ring-cloned, and the expression of ASK1 protein was determined by immunoprecipitation (H. Ichijo et al., J. Biol. Chem., 268, 14505, 1993) with antiserum to ASK1. Two independent positive clones were used for the assays with essentially the same results.

Cells were metabolically labeled with a mixture of [³⁵S]methionine and [³⁵S]cysteine in the presence or absence of 100 μM ZnCl₂ for 5 hours. The cellular lysates were then subjected to immunoprecipitation with antiserum to ASK1, SDS-PAGE, and fluorography.

Results are shown in FIG. 7. It was revealed that ASK was highly expressed only when induced by ZnCl2. ASK1(K709R)-transfected cells expressed the recombinant protein in similar amounts.

(2) Effects on Thymidine Incorporation

To investigate the effects of ASK1 on cellular growth, Mv1Lu cells stably transfected with vector alone (FIG. 8, black squires), ASK1 (FIG. 8, black circles), and ASK1(K709R) (FIG. 8, white circles) were incubated in MEM containing 1% fetal bovine serum (FBS) and the indicated concentration of ZnCl₂ for 16 hours. The cells were then pulse-labeled with [³H]thymidine for 1 hour, and [³H] radioactivity incorporation into the DNA was determined using a liquid scintillation counter. Results are shown in FIG. 8.

Drastic inhibition of [³H]thymidine incorporation was observed in the cells transfected with ASK1. In contrast, no inhibition was observed in the cells transfected with the vector alone or ASK1(K709R) vector (FIG. 8). Correlation between dose-dependent inhibition of [³H]thymidine incorporation by ZnCl₂ and the dose-dependent expression and activation of ASK1 was investigated. The ASK1-transfected Mv1Lu cells were treated with the indicated amount of ZnCl₂ for 5 hours, and then the level of ASK1 was determined by immunoprecipitation (FIG. 9, top). Furthermore, the cells were treated with the indicated amount of ZnCl₂ for 5 hours, ASK1 was recovered from the cells by immunoprecipitation and then subjected to the MKK3-MPK2 coupled kinase assay (FIG. 9, bottom). Results showed that the dose-dependent inhibition of [³H]thymidine incorporation by ZnCl₂ correlated well with the dose-dependent expression and activation of ASK1 (FIG. 9).

(3) Effects on Enhancement of SAPK and p38 Kinase Activity

The following experiment was carried out to investigate correlation between ASK1 activity and endogenous SAPK and p38 activation.

Mv1Lu cells stably transfected with ASK1 were incubated with the indicated concentration of ZnCl₂ for 5 hours. To measure the activity of SAPK, each cell extract was subjected to a kinase detection assay (in-gel kinase assay) within a polyacrylamide gel containing c-Jun as a substrate protein according to the method described in S. Matsuda et al., J. Biol. Chem., 270, 12781, 1995. To examine the activity of p38, p38 was immunoprecipitated with polyclonal antibody to p38 (C-20, Santa Cruz) according to the method described in Example 3 except for the presence of 0.1% SDS during the immunoprecipitation. The kinase activity was then detected using ATF2 as a substrate protein. Results are shown in FIG. 10.

It was revealed that endogenous SAPK and p38 were also activated in parallel with the ASK1 activities. (4) Effects on cell morphology and DNA fragmentation

It was revealed that morphological changes (namely, cytoplasmic shrinkage and cellular condensation) were induced within 6 hours after addition of ZnCl₂ when cells were treated with 100 μM ZnCl₂ and ASK1 was continuously expressed (data not shown). These morphological changes were not observed in the cells in which ASK1(K709R) was expressed. Cells were incubated with MEM containing 1% FBS in the presence or absence of 100 μM ZnCl₂ for 26 hours. The typical morphological properties of apoptotic cells, i.e., cytoplasmic shrinkage and cellular condensation, became most evident after induction for long hours (26 hours) (FIG. 11, top).

Whether ASK1 induces the apoptotic cell death was investigated by an in situ staining of cells with the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method (FIG. 11, bottom) as well as by genomic DNA fragmentation. More specifically, Mv1Lu cells transfected with ASK1 were incubated with MEM without FBS in the presence or absence of 100 μM ZnCl₂ for 25 hours and then stained by TUNEL method with a situ cell death detection kit (Boehringer Mannheim) (FIG. 11, bottom), or the total DNA was isolated and subjected to 2% agarose gel electrophoresis (FIG. 12). As a result, apoptosis and DNA fragmentation were observed after induction of ASK1 expression by ZnCl₂ (FIG. 11, bottom, and FIG. 12).

Example 6

ASK1 Activation by TNF-α

In this Example, whether the treatment of cells with TNF-α resulted in the activation of ASK1 was examined. Mv1Lu cells transfected with ASK1 were first treated with 50 μM ZnCl₂ for 5 hours to induce ASK1 expression. The cells were then stimulated with TNF-α (100 ng/ml) for the indicated time. ASK1 immunoprecipitates derived from TNF-α-treated cells were subjected to a coupled kinase assay with MKK3 and kinase-negative p38 (FIG. 13, top and bottom, and FIG. 14).

The results showed that the treatment of cells with TNF-α activated the ASK1 in ASK1-transfected Mv1Lu cells within 5 minutes (FIG. 13, top and bottom). The ASK1 was activated by TNF-α in a dose-dependent manner (FIG. 14).

ASK1-nontransfected 293 cells and A673 cells were treated with TNF-α (100 ng/ml). The results showed that endogenous ASK1 was also activated by TNF-α in other various cell types in which apoptosis is induced by TNF-α (data not shown), including human 293 embryonal kidney cells, A673 rhabdomyosarcoma cells (FIG. 13, bottom), Jurkat T cells, and KB epidermal carcinoma cells (data not shown).

Furthermore, ASK1(K709R) was transiently transfected into 293 cells (FIG. 15) or Jurkat T cells (FIG. 16). Specifically, the experiment was carried out according to the following method. 293 cells (2×10⁶) were transiently transfected with 2 μg of pcDNA3 control vector or pcDNA3-ASK1(K709R) by the use of Tfx-50 (Promega) according to the manufacturer's protocol. Eight hours after transfection, cells were treated with TNF-α (100 ng/ml) with or without 300 nM actinomycin D (ActD) for 16 hours. Apoptotic cells detached from culture plate were collected, and total DNA was isolated and analyzed by 2% agarose gel electrophoresis (FIG. 15).

Furthermore, the pcDNA3-ASK1 (K709R) was transfected into Jurkat cells by DMRIE-C reagent (Life Technologies) together with pHook-1 plasmid (Invitrogen). Further, the pHook-1 plasmid encodes a single-chain antibody fusion protein directed to the hapten phox (4-ethoxymethylene-2-phenyl-2-oxazolin-5-one). Therefore, it is possible to selectively isolate transfected cells with magnetic beads coated with phOx.

ASK1(K709R)-transfected populations of cells (cotransfection efficiency was nearly 100% as determined by β-galactosidase staining) were isolated on phOx-coated magnetic beads with the Capture-Tec kit (Invitrogen), after which the cells were incubated with various concentrations of TNF-α for 5.5 hours. Cytoplasmic small fragmented DNA was isolated as described (Selins, K. & Cohen, J., J. Immunol., 139, 3199, 1987) with minor modifications. Cells (3×10⁶) were lysed with 200 μl of a buffer solution (20 mM Tris-HCl (pH 7.5), 10 mM EDTA, 0.5% Triton X-100). The resulting lysate was incubated with proteinase K (0.2 mg/ml) and RNase N (0.1 mg/ml) at 42° C. for 1 hour. DNA was then purified by phenol-chloroform extraction after ethanol extraction. The extracted cytoplasmic DNA was analyzed by 2% agarose gel electrophoresis (FIG. 16).

The results showed that DNA fragmentation induced by TNF-α was effectively reduced. Further, nontransfected Jurkat cells and isolated Jurkat cells (that were transfected with pHook-1 and control pcDNA3 plasmid) were similarly sensitive to TNF-α in the DNA fragmentation assay (date not shown). This observation suggested that ASK1(K709R) acts as a dominant-negative mutant, and more importantly, that ASK1 is essential for the TNF-α-induced apoptotic response.

3 1 1375 PRT Homo sapiens 1 Met Ser Thr Glu Ala Asp Glu Gly Ile Thr Phe Ser Val Pro Pro Phe 1 5 10 15 Ala Pro Ser Gly Phe Cys Thr Ile Pro Glu Gly Gly Ile Cys Arg Arg 20 25 30 Gly Gly Ala Ala Ala Val Gly Glu Gly Glu Glu His Gln Leu Pro Pro 35 40 45 Pro Pro Pro Gly Ser Phe Trp Asn Val Glu Ser Ala Ala Ala Pro Gly 50 55 60 Ile Gly Cys Pro Ala Ala Thr Ser Ser Ser Ser Ala Thr Arg Gly Arg 65 70 75 80 Gly Ser Ser Val Gly Gly Gly Ser Arg Arg Thr Thr Val Ala Tyr Val 85 90 95 Ile Asn Glu Ala Ser Gln Gly Gln Leu Val Val Ala Glu Ser Glu Ala 100 105 110 Leu Gln Ser Leu Arg Glu Ala Cys Glu Thr Val Gly Ala Thr Leu Glu 115 120 125 Thr Leu His Phe Gly Lys Leu Asp Phe Gly Glu Thr Thr Val Leu Asp 130 135 140 Arg Phe Tyr Asn Ala Asp Ile Ala Val Val Glu Met Ser Asp Ala Phe 145 150 155 160 Arg Gln Pro Ser Leu Phe Tyr His Leu Gly Val Arg Glu Ser Phe Ser 165 170 175 Met Ala Asn Asn Ile Ile Leu Tyr Cys Asp Thr Asn Ser Asp Ser Leu 180 185 190 Gln Ser Leu Lys Glu Ile Ile Cys Gln Lys Asn Thr Met Cys Thr Gly 195 200 205 Asn Tyr Thr Phe Val Pro Tyr Met Ile Thr Pro His Asn Lys Val Tyr 210 215 220 Cys Cys Asp Ser Ser Phe Met Lys Gly Leu Thr Glu Leu Met Gln Pro 225 230 235 240 Asn Phe Glu Leu Leu Leu Gly Pro Ile Cys Leu Pro Leu Val Asp Arg 245 250 255 Phe Ile Gln Leu Leu Lys Val Ala Gln Ala Ser Ser Ser Gln Tyr Phe 260 265 270 Arg Glu Ser Ile Leu Asn Asp Ile Arg Lys Ala Arg Asn Leu Tyr Thr 275 280 285 Gly Lys Glu Leu Ala Ala Glu Leu Ala Arg Ile Arg Gln Arg Val Asp 290 295 300 Asn Ile Glu Val Leu Thr Ala Asp Ile Val Ile Asn Leu Leu Leu Ser 305 310 315 320 Tyr Arg Asp Ile Gln Asp Tyr Asp Ser Ile Val Lys Leu Val Glu Thr 325 330 335 Leu Glu Lys Leu Pro Thr Phe Asp Leu Ala Ser His His His Val Lys 340 345 350 Phe His Tyr Ala Phe Ala Leu Asn Arg Arg Asn Leu Pro Gly Asp Arg 355 360 365 Ala Lys Ala Leu Asp Ile Met Ile Pro Met Val Gln Ser Glu Gly Gln 370 375 380 Val Ala Ser Asp Met Tyr Cys Leu Val Gly Arg Ile Tyr Lys Asp Met 385 390 395 400 Phe Leu Asp Ser Asn Phe Thr Asp Thr Glu Ser Arg Asp His Gly Ala 405 410 415 Ser Trp Phe Lys Lys Ala Phe Glu Ser Glu Pro Thr Leu Gln Ser Gly 420 425 430 Ile Asn Tyr Ala Val Leu Leu Leu Ala Ala Gly His Gln Phe Glu Ser 435 440 445 Ser Phe Glu Leu Arg Lys Val Gly Val Lys Leu Ser Ser Leu Leu Gly 450 455 460 Lys Lys Gly Asn Leu Glu Lys Leu Gln Ser Tyr Trp Glu Val Gly Phe 465 470 475 480 Phe Leu Gly Ala Ser Val Leu Ala Asn Asp His Met Arg Val Ile Gln 485 490 495 Ala Ser Glu Lys Leu Phe Lys Leu Lys Thr Pro Ala Trp Tyr Leu Lys 500 505 510 Ser Ile Val Glu Thr Ile Leu Ile Tyr Lys His Phe Val Lys Leu Thr 515 520 525 Thr Glu Gln Pro Val Ala Lys Gln Glu Leu Val Asp Phe Trp Met Asp 530 535 540 Phe Leu Val Glu Ala Thr Lys Thr Asp Val Thr Val Val Arg Phe Pro 545 550 555 560 Val Leu Ile Leu Glu Pro Thr Lys Ile Tyr Gln Pro Ser Tyr Leu Ser 565 570 575 Ile Asn Asn Glu Val Glu Glu Lys Thr Ile Ser Ile Trp His Val Leu 580 585 590 Pro Asp Asp Lys Lys Gly Ile His Glu Trp Asn Phe Ser Ala Ser Ser 595 600 605 Val Arg Gly Val Ser Ile Ser Lys Phe Glu Glu Arg Cys Cys Phe Leu 610 615 620 Tyr Val Leu His Asn Ser Asp Asp Phe Gln Ile Tyr Phe Cys Thr Glu 625 630 635 640 Leu His Cys Lys Lys Phe Phe Glu Met Val Asn Thr Ile Thr Glu Glu 645 650 655 Lys Gly Arg Ser Thr Glu Glu Gly Asp Cys Glu Ser Asp Leu Leu Glu 660 665 670 Tyr Asp Tyr Glu Tyr Asp Glu Asn Gly Asp Arg Val Val Leu Gly Lys 675 680 685 Gly Thr Tyr Gly Ile Val Tyr Ala Gly Arg Asp Leu Ser Asn Gln Val 690 695 700 Arg Ile Ala Ile Lys Glu Ile Pro Glu Arg Asp Ser Arg Tyr Ser Gln 705 710 715 720 Pro Leu His Glu Glu Ile Ala Leu His Lys His Leu Lys His Lys Asn 725 730 735 Ile Val Gln Tyr Leu Gly Ser Phe Ser Glu Asn Gly Phe Ile Lys Ile 740 745 750 Phe Met Glu Gln Val Pro Gly Gly Ser Leu Tyr Ala Leu Leu Arg Ser 755 760 765 Lys Trp Gly Pro Leu Lys Asp Asn Glu Gln Thr Ile Gly Phe Tyr Thr 770 775 780 Lys Gln Ile Leu Glu Gly Leu Lys Tyr Leu His Asp Asn Gln Ile Val 785 790 795 800 His Arg Asp Ile Lys Gly Asp Asn Val Leu Ile Asn Thr Tyr Ser Gly 805 810 815 Val Leu Lys Ile Ser Asp Phe Gly Thr Ser Lys Arg Leu Ala Gly Ile 820 825 830 Asn Pro Cys Thr Glu Thr Phe Thr Gly Thr Leu Gln Tyr Met Ala Pro 835 840 845 Glu Ile Ile Asp Lys Gly Pro Arg Gly Tyr Gly Lys Ala Ala Asp Ile 850 855 860 Trp Ser Leu Gly Cys Thr Ile Ile Glu Met Ala Thr Gly Lys Pro Pro 865 870 875 880 Phe Tyr Glu Leu Gly Glu Pro Gln Ala Ala Met Phe Lys Val Gly Met 885 890 895 Phe Lys Val His Pro Glu Ile Pro Glu Ser Met Ser Ala Glu Ala Lys 900 905 910 Ala Phe Ile Leu Lys Cys Phe Glu Pro Asp Pro Asp Lys Arg Ala Cys 915 920 925 Ala Asn Asp Leu Leu Val Asp Glu Phe Leu Lys Val Ser Ser Lys Lys 930 935 940 Lys Lys Thr Gln Pro Lys Leu Ser Ala Leu Ser Ala Gly Ser Asn Ala 945 950 955 960 Glu Tyr Leu Arg Ser Ile Ser Leu Pro Val Pro Val Leu Val Glu Asp 965 970 975 Thr Ser Ser Ser Ser Glu Tyr Gly Ser Val Ser Pro Asp Thr Glu Leu 980 985 990 Lys Val Asp Pro Phe Ser Phe Lys Thr Arg Ala Lys Ser Cys Gly Glu 995 1000 1005 Arg Asp Val Lys Gly Ile Arg Thr Leu Phe Leu Gly Ile Pro Asp Glu 1010 1015 1020 Asn Phe Glu Asp His Ser Ala Pro Pro Ser Pro Glu Glu Lys Asp Ser 1025 1030 1035 1040 Gly Phe Phe Met Leu Arg Lys Asp Ser Glu Arg Arg Ala Thr Leu His 1045 1050 1055 Arg Ile Leu Thr Glu Asp Gln Asp Lys Ile Val Arg Asn Leu Met Glu 1060 1065 1070 Ser Leu Ala Gln Gly Ala Glu Glu Pro Lys Leu Lys Trp Glu His Ile 1075 1080 1085 Thr Thr Leu Ile Ala Ser Leu Arg Glu Phe Val Arg Ser Thr Asp Arg 1090 1095 1100 Lys Ile Ile Ala Thr Thr Leu Ser Lys Leu Lys Leu Glu Leu Asp Phe 1105 1110 1115 1120 Asp Ser His Gly Ile Ser Gln Val Gln Val Val Leu Phe Gly Phe Gln 1125 1130 1135 Asp Ala Val Asn Lys Val Leu Arg Asn His Asn Ile Lys Pro His Trp 1140 1145 1150 Met Phe Ala Leu Asp Ser Ile Ile Arg Lys Ala Val Gln Thr Ala Ile 1155 1160 1165 Thr Ile Leu Val Pro Glu Leu Arg Pro His Phe Ser Leu Ala Ser Glu 1170 1175 1180 Ser Asp Thr Ala Asp Gln Glu Asp Leu Asp Val Glu Asp Asp His Glu 1185 1190 1195 1200 Glu Gln Pro Ser Asn Gln Thr Val Arg Arg Pro Gln Ala Val Ile Glu 1205 1210 1215 Asp Ala Val Ala Thr Ser Gly Val Ser Thr Leu Ser Ser Thr Val Ser 1220 1225 1230 His Asp Ser Gln Ser Ala His Arg Ser Leu Asn Val Gln Leu Gly Arg 1235 1240 1245 Met Lys Ile Glu Thr Asn Arg Leu Leu Glu Glu Leu Val Arg Lys Glu 1250 1255 1260 Lys Glu Leu Gln Ala Leu Leu His Arg Ala Ile Glu Glu Lys Asp Gln 1265 1270 1275 1280 Glu Ile Lys His Leu Lys Leu Lys Ser Gln Pro Ile Glu Ile Pro Glu 1285 1290 1295 Leu Pro Val Phe His Leu Asn Ser Ser Gly Thr Asn Ile Glu Asp Ser 1300 1305 1310 Glu Leu Thr Asp Trp Leu Arg Val Asn Gly Ala Asp Glu Asp Thr Ile 1315 1320 1325 Ser Arg Phe Leu Ala Glu Asp Tyr Thr Leu Leu Asp Val Leu Tyr Tyr 1330 1335 1340 Val Thr Arg Asp Asp Leu Lys Cys Leu Arg Leu Arg Gly Gly Met Leu 1345 1350 1355 1360 Cys Thr Leu Trp Lys Ala Ile Ile Asp Phe Arg Asn Lys Gln Thr 1365 1370 1375 2 4533 DNA Homo sapiens CDS (268)..(4392) 2 acccggcttc cccacccctt gtactctaaa ctctgcagag ggcgagcgtg cggccacgga 60 ggcgccgagg aggagcgagc gccgccgggc agcggcgtgc cctcggggga gagggcgccg 120 gagaggaggc ggcggcgcgg cggcgagggc gcggcgcgcg atggcagctg cttagcccgg 180 cgggcgcgga gcagccccga gctgtggctg gccaggcggt gcggctgggc gggggacgcc 240 gccgccgttg ctgcccggcc cggagag atg agc acg gag gcg gac gag ggc atc 294 Met Ser Thr Glu Ala Asp Glu Gly Ile 1 5 act ttc tct gtg cca ccc ttc gcc ccc tcg ggc ttc tgc acc atc ccc 342 Thr Phe Ser Val Pro Pro Phe Ala Pro Ser Gly Phe Cys Thr Ile Pro 10 15 20 25 gag ggc ggc atc tgc agg agg gga gga gcg gcg gcg gtg ggc gag ggc 390 Glu Gly Gly Ile Cys Arg Arg Gly Gly Ala Ala Ala Val Gly Glu Gly 30 35 40 gag gag cac cag ctg cca ccg ccg ccg ccg ggc agt ttc tgg aac gtg 438 Glu Glu His Gln Leu Pro Pro Pro Pro Pro Gly Ser Phe Trp Asn Val 45 50 55 gag agc gcc gct gcc cct ggc atc ggt tgt ccg gcg gcc acc tcc tcg 486 Glu Ser Ala Ala Ala Pro Gly Ile Gly Cys Pro Ala Ala Thr Ser Ser 60 65 70 agc agt gcc acc cga ggc cgg ggc agc tct gtt ggc ggg ggc agc cga 534 Ser Ser Ala Thr Arg Gly Arg Gly Ser Ser Val Gly Gly Gly Ser Arg 75 80 85 cgg acc acg gtg gca tat gtg atc aac gaa gcg agc caa ggg caa ctg 582 Arg Thr Thr Val Ala Tyr Val Ile Asn Glu Ala Ser Gln Gly Gln Leu 90 95 100 105 gtg gtg gcc gag agc gag gcc ctg cag agc ttg cgg gag gcg tgc gag 630 Val Val Ala Glu Ser Glu Ala Leu Gln Ser Leu Arg Glu Ala Cys Glu 110 115 120 aca gtg ggc gcc acc ctg gaa acc ctg cat ttt ggg aaa ctc gac ttt 678 Thr Val Gly Ala Thr Leu Glu Thr Leu His Phe Gly Lys Leu Asp Phe 125 130 135 gga gaa acc acc gtg ctg gac cgc ttt tac aat gca gat att gcg gtg 726 Gly Glu Thr Thr Val Leu Asp Arg Phe Tyr Asn Ala Asp Ile Ala Val 140 145 150 gtg gag atg agc gat gcc ttc cgg cag ccg tcc ttg ttt tac cac ctt 774 Val Glu Met Ser Asp Ala Phe Arg Gln Pro Ser Leu Phe Tyr His Leu 155 160 165 ggg gtg aga gaa agt ttc agc atg gcc aac aac atc atc ctc tac tgc 822 Gly Val Arg Glu Ser Phe Ser Met Ala Asn Asn Ile Ile Leu Tyr Cys 170 175 180 185 gat act aac tcg gac tct ctg cag tca ctg aag gaa atc att tgc cag 870 Asp Thr Asn Ser Asp Ser Leu Gln Ser Leu Lys Glu Ile Ile Cys Gln 190 195 200 aag aat act atg tgc act ggg aac tac acc ttt gtt cct tac atg ata 918 Lys Asn Thr Met Cys Thr Gly Asn Tyr Thr Phe Val Pro Tyr Met Ile 205 210 215 act cca cat aac aaa gtc tac tgc tgt gac agc agc ttc atg aag ggg 966 Thr Pro His Asn Lys Val Tyr Cys Cys Asp Ser Ser Phe Met Lys Gly 220 225 230 ttg aca gag ctc atg caa ccg aac ttc gag ctg ctt ctt gga ccc atc 1014 Leu Thr Glu Leu Met Gln Pro Asn Phe Glu Leu Leu Leu Gly Pro Ile 235 240 245 tgc tta cct ctt gtg gat cgt ttt att caa ctt ttg aag gtg gca caa 1062 Cys Leu Pro Leu Val Asp Arg Phe Ile Gln Leu Leu Lys Val Ala Gln 250 255 260 265 gca agt tct agc cag tac ttc cgg gaa tct ata ctc aat gac atc agg 1110 Ala Ser Ser Ser Gln Tyr Phe Arg Glu Ser Ile Leu Asn Asp Ile Arg 270 275 280 aaa gct cgt aat tta tac act ggt aaa gaa ttg gca gct gag ttg gca 1158 Lys Ala Arg Asn Leu Tyr Thr Gly Lys Glu Leu Ala Ala Glu Leu Ala 285 290 295 aga att cgg cag cga gta gat aat atc gaa gtc ttg aca gca gat att 1206 Arg Ile Arg Gln Arg Val Asp Asn Ile Glu Val Leu Thr Ala Asp Ile 300 305 310 gtc ata aat ctg tta ctt tcc tac aga gat atc cag gac tat gat tct 1254 Val Ile Asn Leu Leu Leu Ser Tyr Arg Asp Ile Gln Asp Tyr Asp Ser 315 320 325 att gtg aag ctg gta gag act tta gaa aaa ctg cca acc ttt gat ttg 1302 Ile Val Lys Leu Val Glu Thr Leu Glu Lys Leu Pro Thr Phe Asp Leu 330 335 340 345 gcc tcc cat cac cat gtg aag ttt cat tat gca ttt gca ctg aat agg 1350 Ala Ser His His His Val Lys Phe His Tyr Ala Phe Ala Leu Asn Arg 350 355 360 aga aat ctc cct ggt gac aga gca aaa gct ctt gat att atg att ccc 1398 Arg Asn Leu Pro Gly Asp Arg Ala Lys Ala Leu Asp Ile Met Ile Pro 365 370 375 atg gtg caa agc gaa gga caa gtt gct tca gat atg tat tgc cta gtt 1446 Met Val Gln Ser Glu Gly Gln Val Ala Ser Asp Met Tyr Cys Leu Val 380 385 390 ggt cga atc tac aaa gat atg ttt ttg gac tct aat ttc acg gac act 1494 Gly Arg Ile Tyr Lys Asp Met Phe Leu Asp Ser Asn Phe Thr Asp Thr 395 400 405 gaa agc aga gac cat gga gct tct tgg ttc aaa aag gca ttt gaa tct 1542 Glu Ser Arg Asp His Gly Ala Ser Trp Phe Lys Lys Ala Phe Glu Ser 410 415 420 425 gag cca aca cta cag tca gga att aat tat gcg gtc ctc ctc ctg gca 1590 Glu Pro Thr Leu Gln Ser Gly Ile Asn Tyr Ala Val Leu Leu Leu Ala 430 435 440 gct gga cac cag ttt gaa tct tcc ttt gag ctc cgg aaa gtt ggg gtg 1638 Ala Gly His Gln Phe Glu Ser Ser Phe Glu Leu Arg Lys Val Gly Val 445 450 455 aag cta agt agt ctt ctt ggt aaa aag gga aac ttg gaa aaa ctc cag 1686 Lys Leu Ser Ser Leu Leu Gly Lys Lys Gly Asn Leu Glu Lys Leu Gln 460 465 470 agc tac tgg gaa gtt gga ttt ttt ctg ggg gcc agc gtc cta gcc aat 1734 Ser Tyr Trp Glu Val Gly Phe Phe Leu Gly Ala Ser Val Leu Ala Asn 475 480 485 gac cac atg aga gtc att caa gca tct gaa aag ctt ttt aaa ctg aag 1782 Asp His Met Arg Val Ile Gln Ala Ser Glu Lys Leu Phe Lys Leu Lys 490 495 500 505 aca cca gca tgg tac ctc aag tct att gta gag aca att ttg ata tat 1830 Thr Pro Ala Trp Tyr Leu Lys Ser Ile Val Glu Thr Ile Leu Ile Tyr 510 515 520 aag cat ttt gtg aaa ctg acc aca gaa cag cct gtg gcc aag caa gaa 1878 Lys His Phe Val Lys Leu Thr Thr Glu Gln Pro Val Ala Lys Gln Glu 525 530 535 ctt gtg gac ttt tgg atg gat ttc ctg gtc gag gcc aca aag aca gat 1926 Leu Val Asp Phe Trp Met Asp Phe Leu Val Glu Ala Thr Lys Thr Asp 540 545 550 gtt act gtg gtt agg ttt cca gta tta ata tta gaa cca acc aaa atc 1974 Val Thr Val Val Arg Phe Pro Val Leu Ile Leu Glu Pro Thr Lys Ile 555 560 565 tat caa cct tct tat ttg tct atc aac aat gaa gtt gag gaa aag aca 2022 Tyr Gln Pro Ser Tyr Leu Ser Ile Asn Asn Glu Val Glu Glu Lys Thr 570 575 580 585 atc tct att tgg cac gtg ctt cct gat gac aag aaa ggt ata cat gag 2070 Ile Ser Ile Trp His Val Leu Pro Asp Asp Lys Lys Gly Ile His Glu 590 595 600 tgg aat ttt agt gcc tct tct gtc agg gga gtg agt att tct aaa ttt 2118 Trp Asn Phe Ser Ala Ser Ser Val Arg Gly Val Ser Ile Ser Lys Phe 605 610 615 gaa gaa aga tgc tgc ttt ctt tat gtg ctt cac aat tct gat gat ttc 2166 Glu Glu Arg Cys Cys Phe Leu Tyr Val Leu His Asn Ser Asp Asp Phe 620 625 630 caa atc tat ttc tgt aca gaa ctt cat tgt aaa aag ttt ttt gag atg 2214 Gln Ile Tyr Phe Cys Thr Glu Leu His Cys Lys Lys Phe Phe Glu Met 635 640 645 gtg aac acc att acc gaa gag aag ggg aga agc aca gag gaa gga gac 2262 Val Asn Thr Ile Thr Glu Glu Lys Gly Arg Ser Thr Glu Glu Gly Asp 650 655 660 665 tgt gaa agt gac ttg ctg gag tat gac tat gaa tat gat gaa aat ggt 2310 Cys Glu Ser Asp Leu Leu Glu Tyr Asp Tyr Glu Tyr Asp Glu Asn Gly 670 675 680 gac aga gtc gtt tta gga aaa ggc act tat ggg ata gtc tac gca ggt 2358 Asp Arg Val Val Leu Gly Lys Gly Thr Tyr Gly Ile Val Tyr Ala Gly 685 690 695 cgg gac ttg agc aac caa gtc aga att gct att aag gaa atc cca gag 2406 Arg Asp Leu Ser Asn Gln Val Arg Ile Ala Ile Lys Glu Ile Pro Glu 700 705 710 aga gac agc aga tac tct cag ccc ctg cat gaa gaa ata gca ttg cat 2454 Arg Asp Ser Arg Tyr Ser Gln Pro Leu His Glu Glu Ile Ala Leu His 715 720 725 aaa cac ctg aag cac aaa aat att gtc cag tat ctg ggc tct ttc agt 2502 Lys His Leu Lys His Lys Asn Ile Val Gln Tyr Leu Gly Ser Phe Ser 730 735 740 745 gag aat ggt ttc att aaa atc ttc atg gag cag gtc cct gga gga agt 2550 Glu Asn Gly Phe Ile Lys Ile Phe Met Glu Gln Val Pro Gly Gly Ser 750 755 760 ctt tat gct ctc ctt cgt tcc aaa tgg ggt cca tta aaa gac aat gag 2598 Leu Tyr Ala Leu Leu Arg Ser Lys Trp Gly Pro Leu Lys Asp Asn Glu 765 770 775 caa aca att ggc ttt tat aca aag caa ata ctg gaa gga tta aaa tat 2646 Gln Thr Ile Gly Phe Tyr Thr Lys Gln Ile Leu Glu Gly Leu Lys Tyr 780 785 790 ctc cat gac aat cag ata gtt cac cgg gac ata aag ggt gac aat gtg 2694 Leu His Asp Asn Gln Ile Val His Arg Asp Ile Lys Gly Asp Asn Val 795 800 805 ttg att aat acc tac agt ggt gtt ctc aag atc tct gac ttc gga aca 2742 Leu Ile Asn Thr Tyr Ser Gly Val Leu Lys Ile Ser Asp Phe Gly Thr 810 815 820 825 tca aag agg ctt gct ggc ata aac ccc tgt act gaa act ttt act ggt 2790 Ser Lys Arg Leu Ala Gly Ile Asn Pro Cys Thr Glu Thr Phe Thr Gly 830 835 840 acc ctc cag tat atg gca cca gaa ata ata gat aaa gga cca aga ggc 2838 Thr Leu Gln Tyr Met Ala Pro Glu Ile Ile Asp Lys Gly Pro Arg Gly 845 850 855 tac gga aaa gca gca gac atc tgg tct ctg ggc tgt aca atc att gaa 2886 Tyr Gly Lys Ala Ala Asp Ile Trp Ser Leu Gly Cys Thr Ile Ile Glu 860 865 870 atg gcc aca gga aaa ccc cca ttt tat gaa ctg gga gaa cca caa gca 2934 Met Ala Thr Gly Lys Pro Pro Phe Tyr Glu Leu Gly Glu Pro Gln Ala 875 880 885 gct atg ttc aag gtg gga atg ttt aaa gtc cac cct gag atc cca gag 2982 Ala Met Phe Lys Val Gly Met Phe Lys Val His Pro Glu Ile Pro Glu 890 895 900 905 tcc atg tct gca gag gcc aag gca ttc ata ctg aaa tgt ttt gaa cca 3030 Ser Met Ser Ala Glu Ala Lys Ala Phe Ile Leu Lys Cys Phe Glu Pro 910 915 920 gat cct gac aag aga gcc tgt gct aac gac ttg ctt gtt gat gag ttt 3078 Asp Pro Asp Lys Arg Ala Cys Ala Asn Asp Leu Leu Val Asp Glu Phe 925 930 935 tta aaa gtt tca agc aaa aag aaa aag aca caa cct aag ctt tca gct 3126 Leu Lys Val Ser Ser Lys Lys Lys Lys Thr Gln Pro Lys Leu Ser Ala 940 945 950 ctt tca gct gga tca aat gca gaa tat ctc agg agt ata tcc ttg ccg 3174 Leu Ser Ala Gly Ser Asn Ala Glu Tyr Leu Arg Ser Ile Ser Leu Pro 955 960 965 gta cct gtg ctg gtg gag gac acc agc agc agc agt gag tac ggc tca 3222 Val Pro Val Leu Val Glu Asp Thr Ser Ser Ser Ser Glu Tyr Gly Ser 970 975 980 985 gtt tca ccc gac acg gag ttg aaa gtg gac ccc ttc tct ttc aaa aca 3270 Val Ser Pro Asp Thr Glu Leu Lys Val Asp Pro Phe Ser Phe Lys Thr 990 995 1000 aga gcc aag tcc tgc gga gaa aga gat gtc aag gga att cgg aca ctc 3318 Arg Ala Lys Ser Cys Gly Glu Arg Asp Val Lys Gly Ile Arg Thr Leu 1005 1010 1015 ttt ttg ggc att cca gat gag aat ttt gaa gat cac agt gct cct cct 3366 Phe Leu Gly Ile Pro Asp Glu Asn Phe Glu Asp His Ser Ala Pro Pro 1020 1025 1030 tcc cct gaa gaa aaa gat tct gga ttc ttc atg ctg agg aag gac agt 3414 Ser Pro Glu Glu Lys Asp Ser Gly Phe Phe Met Leu Arg Lys Asp Ser 1035 1040 1045 gag agg cga gct acc ctt cac agg atc ctg acg gaa gac caa gac aaa 3462 Glu Arg Arg Ala Thr Leu His Arg Ile Leu Thr Glu Asp Gln Asp Lys 1050 1055 1060 1065 att gtg aga aac cta atg gaa tct tta gct cag ggg gct gaa gaa ccg 3510 Ile Val Arg Asn Leu Met Glu Ser Leu Ala Gln Gly Ala Glu Glu Pro 1070 1075 1080 aaa cta aaa tgg gaa cac atc aca acc ctc att gca agc ctc aga gaa 3558 Lys Leu Lys Trp Glu His Ile Thr Thr Leu Ile Ala Ser Leu Arg Glu 1085 1090 1095 ttt gtg aga tcc act gac cga aaa atc ata gcc acc aca ctg tca aag 3606 Phe Val Arg Ser Thr Asp Arg Lys Ile Ile Ala Thr Thr Leu Ser Lys 1100 1105 1110 ctg aaa ctg gag ctg gac ttc gac agc cat ggc att agc caa gtc cag 3654 Leu Lys Leu Glu Leu Asp Phe Asp Ser His Gly Ile Ser Gln Val Gln 1115 1120 1125 gtg gta ctc ttt ggt ttt caa gat gct gtc aat aaa gtt ctt cgg aat 3702 Val Val Leu Phe Gly Phe Gln Asp Ala Val Asn Lys Val Leu Arg Asn 1130 1135 1140 1145 cat aac atc aag ccg cac tgg atg ttt gcc tta gac agt atc att cgg 3750 His Asn Ile Lys Pro His Trp Met Phe Ala Leu Asp Ser Ile Ile Arg 1150 1155 1160 aag gcg gta cag aca gcc att acc atc ctg gtt cca gaa cta agg cca 3798 Lys Ala Val Gln Thr Ala Ile Thr Ile Leu Val Pro Glu Leu Arg Pro 1165 1170 1175 cat ttc agc ctt gca tct gag agt gat act gct gat caa gaa gac ttg 3846 His Phe Ser Leu Ala Ser Glu Ser Asp Thr Ala Asp Gln Glu Asp Leu 1180 1185 1190 gat gta gaa gat gac cat gag gaa cag cct tca aat caa act gtc cga 3894 Asp Val Glu Asp Asp His Glu Glu Gln Pro Ser Asn Gln Thr Val Arg 1195 1200 1205 aga cct cag gct gtc att gaa gat gct gtg gct acc tca ggc gtg agc 3942 Arg Pro Gln Ala Val Ile Glu Asp Ala Val Ala Thr Ser Gly Val Ser 1210 1215 1220 1225 acg ctc agt tct act gtg tct cat gat tcc cag agt gct cac cgg tca 3990 Thr Leu Ser Ser Thr Val Ser His Asp Ser Gln Ser Ala His Arg Ser 1230 1235 1240 ctg aat gta cag ctt gga agg atg aaa ata gaa acc aat aga tta ctg 4038 Leu Asn Val Gln Leu Gly Arg Met Lys Ile Glu Thr Asn Arg Leu Leu 1245 1250 1255 gaa gaa ttg gtt cgg aaa gag aaa gaa tta caa gca ctc ctt cat cga 4086 Glu Glu Leu Val Arg Lys Glu Lys Glu Leu Gln Ala Leu Leu His Arg 1260 1265 1270 gct att gaa gaa aaa gac caa gaa att aaa cac ctg aag ctt aag tcc 4134 Ala Ile Glu Glu Lys Asp Gln Glu Ile Lys His Leu Lys Leu Lys Ser 1275 1280 1285 caa ccc ata gaa att cct gaa ttg cct gta ttt cat cta aat tct tct 4182 Gln Pro Ile Glu Ile Pro Glu Leu Pro Val Phe His Leu Asn Ser Ser 1290 1295 1300 1305 ggc aca aat att gaa gat tct gaa ctt acc gac tgg ctg aga gtg aat 4230 Gly Thr Asn Ile Glu Asp Ser Glu Leu Thr Asp Trp Leu Arg Val Asn 1310 1315 1320 gga gct gat gaa gac act ata agc cgg ttt ttg gct gaa gat tat aca 4278 Gly Ala Asp Glu Asp Thr Ile Ser Arg Phe Leu Ala Glu Asp Tyr Thr 1325 1330 1335 cta ttg gat gtt ctc tac tat gtt aca cgt gat gac tta aaa tgc ttg 4326 Leu Leu Asp Val Leu Tyr Tyr Val Thr Arg Asp Asp Leu Lys Cys Leu 1340 1345 1350 aga cta agg gga ggg atg ctg tgc aca ctg tgg aag gct atc att gac 4374 Arg Leu Arg Gly Gly Met Leu Cys Thr Leu Trp Lys Ala Ile Ile Asp 1355 1360 1365 ttt cga aac aaa cag act tgactgttgc tcaatctaat cttcgatgga 4422 Phe Arg Asn Lys Gln Thr 1370 1375 aattctaaaa attaatacag agctgatctt cttgggggtg ggaaaatcga agggagagga 4482 gaaaggcgct gcactttaaa tccagtattt gtttactcat gttaaaaaaa a 4533 3 16 PRT Homo sapiens 3 Thr Glu Glu Lys Gly Arg Ser Thr Glu Glu Gly Asp Cys Glu Ser Asp 1 5 10 15 

What is claimed is:
 1. An isolated protein comprising the amino acid sequence of SEQ ID NO:
 1. 2. An isolated protein comprising the amino acid sequence of SEQ ID NO: 1 that has one addition, one insertion, one substitution, and/or one deletion and that enhances SEK1 kinase activity and/or MKK3 kinase activity.
 3. An isolated protein consisting essentially of the amino acid sequence of SEQ ID NO:
 1. 4. An isolated protein comprising the amino acid sequence of SEQ ID NO: 1 which has one addition, one insertion, one substitution, and/or one deletion and lacks protein kinase activity.
 5. An isolated protein as claimed in claim 4 having substitution K709R.
 6. An isolated nucleotide sequence encoding a protein according to claim
 1. 7. An isolated nucleotide sequence according to claim 6, which comprises the DNA sequence of SEQ ID NO:
 2. 8. An isolated nucleotide sequence encoding a protein of claim
 4. 9. A vector comprising a nucleotide sequence of claim
 6. 10. A vector comprising a nucleotide sequence of claim
 8. 11. A vector as claimed in claim 9, selected from the group consisting of plasmid vectors, virus vectors and liposome vectors.
 12. A host cell transformed with a vector of claim
 9. 13. A host cell as claimed in claim 12 selected from the group consisting of Escherichia coli, yeast cells, insect cells, COS cells, mink pulmonary epithelial cells, lymphocytes, fibroblasts, NIH/3T3 cells, CHO cells, blood cells and tumor cells.
 14. A method for producing a protein that has protein kinase activity and enhances SEK1 kinase activity and/or MKK3 kinase activity, which comprises culturing host cells of claim 12 and isolating said protein from the culture product.
 15. An agent comprising a protein according to claim 1 and a pharmaceutically acceptable carrier.
 16. A gene therapeutic agent for use in the treatment of malignant tumors, comprising (A) a vector of claim 9 and (B) a pharmaceutically acceptable carrier.
 17. A peptide consisting of the amino acid sequence of 654-669 of SEQ ID NO:
 1. 18. An isolated protein comprising the amino acid sequence 678 to 936 of SEQ ID NO:1, wherein said isolated protein has SEK1 kinase activity and/or MKK3 kinase activity.
 19. An isolated nucleotide sequence encoding a protein according to claim
 2. 20. An isolated nucleotide sequence encoding a protein according to claim
 5. 21. An isolated nucleotide sequence encoding a protein according to claim
 18. 22. An agent comprising a protein according to claim 2 and a pharmaceutically acceptable carrier.
 23. An agent comprising a vector comprising the nucleotide sequence of claim 19 and a pharmaceutically acceptable carrier.
 24. An agent comprising a nucleotide sequence of claim 6 and a pharmaceutically acceptable carrier.
 25. An agent comprising a nucleotide sequence of claim 19 and a pharmaceutically acceptable carrier. 